[TechAssist] Acer 7156S Computer monitor Shut Down.
- From: Dennis Viereck <wa6ati@xxxxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Mon, 07 Jan 2002 14:38:48 -0800
Good afternoon group:
I have an Acer Monitor, model 7156S, that died. I don't work on many of these
but I thought that I would run this past those computer monitor specialists.
This one shuts down after 2 seconds. After some troubleshooting I found that
Q316 was shorted between Drain and Source. This appears to be part of the boost
circuit for the High voltage if I remove Q316 the 50 vdc source at the input of
L304 checks fine with no ripple. In fact High voltage will come up and the
monitor will operate, but only at 12.3 KV highvoltage. The waveform at Q302(C)
was perfect in shape but lower amplitude which was obvious due to the lower B+.
I replaced the defective Q315 with the exact replacement of a IRF540. The
monitor returned to its normal operating condition. Waveform at Q302(C) was
perfect
with Q302 & Q316 running just warm to the touch. I tried different screen
resolutions during this test and all seemed to be perfectly normal.
The monitor operated fine for 45 minutes then shut down again. Again Q316 is
shorted between drain & source. No other damage occurred to the 50 vdc power
supply. The gate drive to Q316 is still normal. I can remove Q316 and I get
about 12KV high voltage for hours. I have the same conditions as I had the first
time I replaced Q316.
Does anyone out there know what why this device might have failed? If I did not
know any better I thought that I was looking at infant mortality of this
replacement component. I have another one ordered but before I replace it again
I thought I would see if anyone out there has already the same experience. No
reason to reinvent the wheel.
Dennis Viereck
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